Analyses on Magnetic Nonlinear Coupled Oscillations in Air Gap of a Generator Rotor System

By applying the extended Lagrange-Maxwell equation and considering the magnetic saturation, the magnetic energy in the air gap of the generator is acquired in analytic form, and the differential equations with periodic coefficients of a rotor system are established. It is shown that the magnetic saturation is one of the factors, which causes electromagnetic moments with double frequencies. The first approximation solution and its corresponding steady-state solution of the primary parametric resonance are obtained. The effect of the electromagnetic parameter in the rotor system on the resonance characteristics is analyzed. Some new phenomena and characteristics are revealed.